The accurate positioning of the alignment mark is key to wafer bonding accuracy. To improve the accuracy, speed and adaptability of the alignment mark positioning algorithm, a high-precision alignment mark positioning algorithm based on edge detection and fitting positioning is proposed. The method combines the hierarchical pyramid model to locate the alignment mark stepwise, and achieve the pixel-level coarse positioning result of the target area. According to the coarse positioning result of the target area, the method combines the Canny detector and the improved Gaussian fitting method. In this way, the sub-pixel contour of the alignment mark is fitted. On this basis, the center position of alignment mark is quickly fitted by the center symmetrical alignment mark feature and the improved least square method to realize accurate positioning of the alignment mark. The effectiveness of the method is evaluated through experiments. Results show that the proposed alignment mark positioning algorithm can locate the target area quickly while the repeat positioning error is about 0. 06 μm, which satisfies the requirements of wafer bonding alignment in terms of accuracy, speed and adaptability.